ORCID
- Taofik Adeiza Momoh: 0000-0002-5798-4640
Abstract
Aquaculture continues to expand as a vital contributor to global food security, yet this growth introduces new challenges including the need to replace fishmeal with plant-based ingredients without compromising intestinal health. In Atlantic salmon aquaculture, one of the main constraints to plant protein inclusion is soybean meal-induced enteritis (SBMIE), a diet-related inflammatory condition that impairs mucosal function. Meanwhile, the use of functional feed additives such as those derived from brewers’ yeast (Saccharomyces cerevisiae) have emerged as a promising strategy to mitigate such diet-induced pathologies and support immune regulation. This thesis investigates the efficacy of structurally distinct brewers’ yeast-derived additives, including purified β-glucan (PβG; 0.02%), nucleotide-rich cytosolic yeast extract (YE; 1% and 2.5%), and whole yeast cell wall (WYCW; 0.2%) in modulating intestinal function and mitigating SBMIE in Atlantic salmon (Salmo salar) parr.To this effect, three in vivo feeding trials were conducted under controlled conditions to simulate key production-relevant stressors. The first trial assessed the impact of dietary PβG and WYCW under non-challenge conditions over a four-week period. Both additives modulated mucosal architecture and epithelial function without affecting growth performance. Notably, 0.02% PβG increased microvilli length and density, and upregulated tight junction and mucin-related genes, while 0.2% WYCW increased goblet cell abundance, suggesting additive-specific benefits to barrier function.The second trial evaluated whether these yeast fractions could mitigate SBMIE. Over eight weeks, fish were fed a 30% soybean meal (SBM) diet supplemented with either 0.02% PβG, 1% YE (YE1), or 2.5% YE (YE2.5). Relative to the positive control, both PβG and YE1 significantly improved intestinal histology, including preserved mucosal folds, relatively intact supranuclear vacuoles, and reduced microvilli damage. Gene expression analysis indicated reduced epithelial stress and enhanced regenerative capacity in these groups. Although, the higher 2.5% YE dose provided only moderate additional benefit, highlighting the importance of dose optimisation.A third trial examined the functional relevance of β-glucan supplementation using an ex vivo pathogen adhesion model. Following a five-week dietary intervention, intestines from fish fed 0.02% PβG showed reduced Aeromonas salmonicida attachment, along with preserved tissue structure and lower local inflammation. Systemic immune analysis revealed increased expression of anti-inflammatory and antimicrobial markers in the head kidney and increased mucosal gene activity in the skin, suggesting coordinated cross-tissue responses.Together, the results demonstrate that yeast-derived additives exert targeted and context-sensitive effects on mucosal health in Atlantic salmon. This work provides a scientific foundation for integrating yeast-based functional additives into precision nutrition strategies aimed at improving fish health, reducing disease risk, and advancing sustainable aquaculture practices.
Awarding Institution(s)
University of Plymouth
Supervisor
Daniel Merrifield, Victor Kuri
Document Type
Thesis
Publication Date
2025
Embargo Period
2025-11-06
Deposit Date
November 2025
Additional Links
Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License
Recommended Citation
Momoh, T. (2025) Evaluating the efficacy of brewers’ yeast-derived functional feed additives in mitigating soybean meal-induced enteritis in Atlantic salmon. Thesis. University of Plymouth. Available at: https://doi.org/10.24382/gmx3-3q72
